Capillary dialyzers are widely used for blood purification in patients suffering from renal insufficiency, i.e., for treatment of the patients by hemodialysis, hemodiafiltration or hemofiltration.
The devices generally consist of a casing comprising a tubular section with end caps capping the mouths of the tubular section. A bundle of hollow fiber membranes is arranged in the casing in a way that a seal is provided between the first flow space formed by the fiber cavities and a second flow space surrounding the membranes on the outside. Examples of such devices are disclosed in EP 0 844 015 A2, EP 0 305 687 A1, and WO 01/60477 A2.
One important factor influencing performance of the device is the structure of the bundle of hollow fiber membranes. Several proposals for improving mass transfer between the flow spaces within the device by optimizing the structure of the bundle of hollow fiber membranes have been made:
DE 28 51 687 C2 discloses hollow, semi-permeable fibers having crimps with an average crimp period of less than 5 cm and a crimp amplitude of 15-250 μm. According to the reference, the relatively low amplitude crimps enable good fluid dispersion through a bundle comprising substantially parallel-oriented hollow fibers.
U.S. Pat. No. 3,616,928 A discloses a filter device comprising a plurality of hollow fibers aligned substantially parallel to one another in which each hollow fiber is crimped along its longitudinal axis such that it comprises a plurality of irregular bends.
JP 02/258035 A discloses a filter device comprising a bundle of hollow fibers having an outer diameter R of 200 to 500 μm; and 1 to 3.5 crimps per cm having a crimp amplitude L of 0.65*R≤L≤R+50 μm.
EP 1 257 333 A1 discloses a filter device, preferably for hemodialysis, that consists of a cylindrical filter housing and a bundle of curled hollow fibers arranged in the filter housing. Each curled hollow fiber is provided with a sinusoidal texture and a wavelength defined by means of certain limits. The packing density of the fibers within the housing is in the range of from 60.5 to 70%, relative to the usable cross-section area of the housing which is calculated by multiplying the cross-section area by 0.907.
There is a continuing desire to further improve such capillary dialyzers, e.g., in terms of performance, efficiency, reliability, safety, handling, and other properties.